1. Sensation and Perception
Prepared by Michael J. Renner, Ph.D.
These slides ©2002 Prentice Hall Psychology Publishing.

2. Sensation and Perception
Sensation: The detection of physical energy emitted or reflected by physical objects; it occurs when energy in the external environment or the body stimulates receptors in the sense organs.
Perception: The process by which the brain organizes and interprets sensory information.

3. Ambiguous Figure
Colored surface can be either the outside front surface or the inside back surface
Cannot simultaneously be both
Brain can interpret the ambiguous cues two different ways
After figure on p 150, from
Wade, C., & Tavris, C. (2002). Invitation to Psychology, 2nd Ed. Upper Saddle River, NJ: Prentice Hall.

4. The Riddle of Separate Sensations
Sense Receptors: Specialized neurons that convert physical energy from the environment or the body into electrical energy that can be transmitted as nerve impulses to the brain.
Doctrine of Specific Nerve Energies: Different sensory modalities exist because signals received by the sense organs stimulate different nerve pathways leading to different areas of the brain.

5. Measuring the Senses Absolute Threshold
The smallest quantity of physical energy that can be reliably detected by an observer
Difference Threshold
The smallest difference in stimulation that can be reliably detected by an observer when two stimuli are compared; also called Just Noticeable Difference (JND).

6. Signal Detection Theory
Holds that responses in a detection task depend on a sensory process and a decision process.
These may vary with a person’s motivation, alertness, and expectations
Not
Present
Present
Hit
False Alarm
Miss
Correct Rejection
Detection No
Detection

7. Absolute Sensory Thresholds
Vision: A single candle flame from 30 miles on a dark, clear night
Hearing: The tick of a watch from 20 feet in total quiet
Smell: 1 drop of perfume in a 3-room apartment
Touch: The wing of a bee on your cheek, dropped from 1 cm
Taste: 1 tsp. Sugar in 2 gal. water

8. Absolute Sensory Thresholds
Despite our impressive sensory skills, our senses are tuned to a narrow band of physical energies.
Other species can detect signals that we cannot.

9. Sensory Adaptations
Sensory Adaptation: The reduction or disappearance of sensory responsiveness that occurs when stimulation is unchanging or repetitious.
Sensory Deprivation: The absence of normal levels of sensory stimulation.

10. Sensory Overload
Selective Attention: The focusing of attention on selected aspects of the environment and the blocking out of others.
Protects us from being overwhelmed

11. Vision What We See An Eye on the World
Why the Visual System is Not a Camera
How We See Colors
Constructing the Visual World

12. What We See
Hue: The dimension of visual experience specified by color names and related to the wavelength of light.
Saturation: Vividness or purity of color; the dimension of visual experience related to the complexity of light waves.
Brightness: Lightness and luminance; the dimension of visual experience related to the amount of light emitted from or reflected by an object (height of wave).

13. An Eye on the World
Retina: Neural tissue lining the back of the eyeball’s interior, which contains the receptors for vision.
Rods: Visual receptors that respond to dim light.
Cones: Visual receptors involved in color vision. Most humans have 3 types of cones.
Dark Adaptation: The process by which visual receptors become maximally sensitive to light.

14. Structures of the Human Eye
Figure 3.4 from:
Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall.
Source:

15. Retinal Image

16. Structures of the Retina
Figure 5.04 from
Wade, C., & Tavris, C. (2002). Invitation to Psychology, 2nd Ed. Upper Saddle River, NJ: Prentice Hall.

19. The Visual System is Not a Camera
Much visual processing is done in the brain.
Some cortical cells respond to lines in specific orientations (e.g. horizontal)
Other cells in the cortex respond to other shapes (e.g., bulls-eyes, spirals, faces)
Feature-detectors: Cells in the visual cortex that are sensitive to specific features of the environment.

20. How We See Colors Trichromatic Theory Opponent Process Theory
Figure 5.04 from
Wade, C., & Tavris, C. (2002). Invitation to Psychology, 2nd Ed. Upper Saddle River, NJ: Prentice Hall.

21. Trichromatic Theory
T. Young (1802) & H. von Helmholtz (1852) both proposed that the eye detects 3 primary colors
Red, blue, & green
All other colors can be derived by combining these three
Figure 3.9 from:
Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall.

22. Opponent-Process Theory
A competing theory of color vision, which assumes that the visual system treats pairs of colors as opposing or antagonistic.
Opponent-Process cells are inhibited by a color, and have a burst of activity when it is removed.

23. Constructing the Visual World
Form Perception
Depth and Distance Perception
Visual Constancies: When Seeing is Believing
Visual Illusions: When Seeing is Misleading

24. Gestalt Principles
Gestalt principles describe the brain’s organization of sensory building blocks into meaningful units and patterns.
Proximity
Closure
Similarity
Continuity
Elements taken from Figure 3.23 from:
Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall.

25. Depth and Distance Perception
Binocular Cues: Visual cues to depth or distance that require the use of both eyes.
Convergence: Turning inward of the eyes, which occurs when they focus on a nearby object
Retinal Disparity: The slight difference in lateral separation between two objects as seen by the left eye and the right eye.
Monocular Cues: Visual cues to depth or distance that can be used by one eye alone.

26. Visual Constancies
The accurate perception of objects as stable or unchanged despite changes in the sensory patterns they produce.
Shape constancy
Location constancy
Size constancy
Brightness constancy
Color constancy

27. Visual Illusions
Illusions are valuable in understanding perception because they are systematic errors.
Illusions provide hints about perceptual strategies
In the Muller-Lyer illusion (above) we tend to perceive the line on the right as slightly longer than the one on the left.
Figure 5.07 from
Wade, C., & Tavris, C. (2002). Invitation to Psychology, 2nd Ed. Upper Saddle River, NJ: Prentice Hall.

28. Fooling the Eye The cats in (a) are the same size
The diagonal lines in (b) are parallel
You can create a “floating fingertip frankfurter” by holding hands as shown, 5-10” in front of face.

29. See Chapter 6 Fun Slides

30. Hearing What We Hear An Ear on the World
Constructing the Auditory World

31. What We Hear
Loudness: The dimension of auditory experience related to the intensity of a pressure wave.
Pitch: The dimension of auditory experience related to the frequency of a pressure wave.
Timbre (pronounced “TAM-bur”): The distinguishing quality of sound; the dimension of auditory experience related to the complexity of the pressure wave.

38. Other Senses Taste: Savory Sensations Smell: The Sense of Scents
Senses of the Skin
The Mystery of Pain
The Environment Within

39. Taste: Savory Sensations
Papillae: Knoblike elevations on the tongue, containing the taste buds (Singular: papilla).
Taste buds: Nests of taste-receptor cells.

40. Smell: The Sense of Scents
Airborne chemical molecules enter the nose and circulate through the nasal cavity.
Vapors can also enter through the mouth and pass into nasal cavity.
Receptors on the roof of the nasal cavity detect these molecules.

41. Smell: The Sense of Scents
Red bars show the people who could identify a substance dropped on the tongue when they were able to smell it

42. Smell: The Sense of Scents
The Blue bars show the people who could identify the substance when they were not able to smell it

43. Senses of the Skin The skin senses include: Touch Warmth Cold Pain
Various others (itch and tickle)

44. Gate-Control Theory of Pain
Experience of pain depends (in part) on whether the pain impulse gets past neurological “gate” in the spinal cord and thus reaches the brain.

45. Neuromatrix Theory of Pain
Theory that the matrix of neurons in the brain is capable of generating pain (and other sensations) in the absence of signals from sensory nerves.

46. The Environment Within
Kinesthesis: The sense of body position and movement of body parts; also called kinesthesia.
Equilibrium: The sense of balance.
Semicircular Canals: Sense organs in the inner ear, which contribute to equilibrium by responding to rotation of the head.

47. Psychological and Cultural Influences on Perception
Needs
Emotions
Expectations
Perceptual Set: A habitual way of perceiving, based on expectations.
Beliefs

48. Puzzles of Perception Subliminal Perception
Extrasensory Perception: Reality or Illusion?

49. Extrasensory Perception
Extrasensory Perception (ESP):
The ability to perceive something without ordinary sensory information
This has not been scientifically demonstrated
Three types of ESP:
Telepathy – Mind-to-mind communication
Clairvoyance – Perception of remote events
Precognition – Ability to see future events